The present invention relates to a distributor type fuel injection pump and, more particularly, to a Lucas type fuel injection pump.
As distributor type fuel injection pumps, a Lucas type fuel injection pump and a Bosch type fuel injection pump have been proposed. The Lucas type pump has a number of advantages such as a reduction in the pressure applied to the cam surface of the cam as compared with the Bosch type pump. However, in the Lucas type fuel injection pump, a rotor rotates as a fuel distributor member only but does not reciprocate. Thus, a spill type delivery control device based on the position control of a spill ring as applied to the Bosch type pump cannot be employed in the Lucas type pump. Then, in the conventional Lucas type pump, a throttle control device for controlling the delivery amount of throttling the fuel from the outlet of the pump is separately provided.
Therefore, the present inventors were able to control the delivery amount of fuel in spill type pump in the same manner as with the Bosch type pump in the Lucas type fuel injection pump by providing a spill ring oil-tightly and slidably mounted on the rotor, the spill ring having a lead groove 10a (hereinbelow referred to as "oblique lead") obliquely cut off on the inner peripheral surface thereof as shown in FIG. 1, forming spill ports in the rotor, the spill ports being connected to the pumping chamber of the pump, and controlling the relative position between the spill ports and the oblique lead.
However, in the Lucas type pump having the oblique lead and the spill ports, when the relative position between the spill ports and the oblique lead is varied by moving the spill rings axially on the rotor, not only the spill starting time at which time the spill ports communicate with the oblique lead but also the spill finishing time at which time the spill ports are closed by the spill ring is varied similar to the spill starting time. Thus, there is a range where the spill period and the fuel suction period overlaps resulting in insufficient fuel suction in this range, and decreased fuel suction efficiency.